Any way to prevent my external startup SSD from converting to APFS?

[Partron22]

Any way to prevent my external startup SSD from converting to APFS as part of System update yet?
Stack Exchange claims it's doable: How to prevent conversion to APFS on High Sierra install.
But has anyone here done it? I expect perhaps some odd problems, maybe security update difficulties or Time Machine freezes. Yet I still have too many ineligible Macs to really want to toss yet in another weird disk format. -Yes, I still run Apps under system 9 emulation.
No time to play right now. Perhaps waiting for 10.14 would be best?

 

[davidlv]

Any way to prevent my external startup SSD from converting to APFS as part of System update yet?
Stack Exchange claims it's doable: How to prevent conversion to APFS on High Sierra install.
But has anyone here done it? I expect perhaps some odd problems, maybe security update difficulties or Time Machine freezes. Yet I still have too many ineligible Macs to really want to toss yet in another weird disk format. -Yes, I still run Apps under system 9 emulation.
No time to play right now. Perhaps waiting for 10.14 would be best?

I found this somewhere on the net; sorry I can't give credit where it is due as I cannot remember where I found it.
It worked for me.
"Install HighSierra without converting to APFS

Make sure the installer file is in the /Applications folder, run the command below from the terminal.

/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO

or
/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --applicationpath /Applications/Install\ macOS\ High\ Sierra.app --agreetolicense --converttoapfs NO --nointeraction

Note: When you enter your password in Terminal, no text will be displayed, giving the impression that Terminal isn’t accepting your input. This is a security feature to ensure prying eyes can’t see your password as it is typed.

You’ll be presented with the license for using macOS High Sierra. You can agree to the license terms by entering a capital A at the prompt.

The startosinstall script will start copying needed files to the target disk (in this example, the current startup disk). You’ll see Terminal counting up to one hundred. When it reaches 100, all the needed files will have been copied, and your Mac will reboot and start the actual installation of the new operating system without converting the startup disk to APFS.

To specify what drive to install macOS High Sierra on, other than the startup drive, you need to add the following to either of the Terminal command lines listed above:

— volume /path to the volume you wish to use

An example for installing macOS High Sierra on a drive named HighSierra without converting the target volume to APFS would be:

sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall –applicationpath /Applications/Install\ macOS\ High\ Sierra.app –converttoapfs NO –volume /Volumes/HighSierra


This would force the installation to occur on a volume named HighSierra. An easy way to enter the actual pathname to the drive you wish to use is to enter the command in Terminal without the actual pathname, so the command would end after — volume (make sure there’s a space after the word volume). Now drag the drive from the Finder and drop it on the Terminal window. Terminal will add the actual pathname to the drive for you. All that’s left to do is press enter or return."

 

[Fishrrman]

OP:
What OS are you running NOW?
Is there anything installed on the SSD -- or, are you "starting fresh" with it?

I don't believe the "automatic conversion to APFS" occurs UNLESS the SSD is internally-mounted.

If you have the SSD connected via USB, I don't believe it will be converted (I have not tried this myself to verify that).

Why don't you try it and tell us what happens?

I will give you my best advice on how to prepare for the upgrade. If you follow this, you will be protected if things don't go as expected.

1. CREATE A CLONED BACKUP of your install AS IT IS NOW. DO NOT skip doing this. Use either CarbonCopyCloner or SuperDuper. BOTH are FREE to download and use for 30 days.
Again, DO NOT skip this important step. If things go wrong, having a bootable cloned backup makes it child's play to "get back to where you once belonged". If you DON'T have a cloned backup, you'll be "up the creek without a paddle".

2. Create a USB flashdrive installer for High Sierra. Do this:
a. Download the HS installer app (but don't RUN it)
b. Download Boot Buddy (small free app) from here:
https://sqwarq.com/boot-buddy/
c. Use Disk Utility to format the flashdrive to Mac OS extended with journaling enabled (flash drive should be 8gb or 16gb)
d. Use Boot Buddy to create the bootable installer -- takes a few clicks of the mouse.

3. Boot from the USB installer. "Aim it" at the SSD drive (you DID create the CCC cloned backup, right?).
You have two choices:
a. Erase what's on the external SSD and start clean
or
b. Install over the existing OS (assuming there is one).

Then, let the installer "go to it".
Observe what it does.
See if it tries to "auto-convert" the drive to APFS.
My -guess- is that it won't.
If that proves true, you're in...

But again -- did I remind you to create that CCC cloned backup before going ahead with the install?

 

[Partron22]

Why don't you try it and tell us what happens?

Likely I will, some Saturday morning when I have free time, which is not now.
I'm running Sierra 10.12.6 just now on main Mac. With iTunes 10.4.1. That's 64 bit, so it'll probably live under High Sierra. Everything is already multiply backed up, and not just with Time Machine.

 

[Partron22]

Did the update on Sunday.
Didn't want anything more complicated than needed so went with the first link I posted. After massive backing up session (Saturday) I used terminal to point the installer at my fully populated external SSD boot drive:

/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO

Had to confirm I really wanted to do the install, and enter my password.
The not clean install went smoothly. It REALLY wanted me to sign up for cloud, so I gave name and pw.
Install took about 45 minutes. Upon reboot, it decided it wanted me to have FaceTime running all the time.
The fix for that annoying dialog is to sign in to FaceTime and disable it. Turned off all the cloud features then signed out of the cloud. Many of the voice files had disappeared, so I went to Sys Prefs Accesibility Speech Customize (at bottom of voices list) and reloaded them.
Boot, bong to last menu bar icon, takes 40 to 45 seconds. Slow by the standard of my 2005 mini in the basement (10.5.11), but acceptable.

Disk utility confirmed my SSD boot drive was Mac OS Extended (Journaled)

After Spotlight got through indexing, my ext SSD read write speeds were within 5MB/S of before the update (write 390 mB/S read 430 mB/S).
Photoshop CS5 still runs.
Pleasingly, iTunes 10.4.1 still runs nicely alongside the iTunes 12.7.4 installed by the update.

Not noticing much difference from 10.12, except that it asks for my password more often.